The present invention relates to a vacuum apparatus such as a sputtering apparatus, a film deposition apparatus or an etching apparatus, and especially to a vacuum apparatus provided with a driving mechanism which transports objects including an object to be treated in the vacuum apparatus.
Conventionally, in a magnetron sputtering apparatus for single substrate processing, which is one of a vacuum apparatus, used for manufacturing information recording disks such as CDs or DVDs, a load lock mechanism is used, which introduces an optical disk substrate made of plastics for depositing a reflection film of a metal or a semi-metal on a surface of the disk substrate into a vacuum vessel from outside using a transportation mechanism. In the sputtering apparatus, such an object to be treated as an optical disk substrate introduced into the vacuum apparatus is transported to a lower portion of a sputtering chamber by the transportation mechanism and is then transported upward into the sputtering chamber by a disk pusher mechanism which reciprocates upward and downward in a lower portion of the sputtering chamber.
In the sputtering apparatuses, both of the load lock mechanism and the disk pusher mechanism described above are provided with a lift mechanism or a driving mechanism, which reciprocates up and down inside the vacuum apparatus transporting objects to be treated. In general the lift mechanisms of the kind employ a high-pressure air cylinder or an oil pressure cylinder. The reasons why such cylinders employ them are described below. In the load lock mechanism, for example, a cylinder rod extends into the vacuum chamber through a vacuum seal from outside of the vacuum chamber. A receptacle provided at an end of the rod is butted and connected to a susceptor for holding the optical disk substrate. The susceptor is then pushed toward an upper wall of the vacuum chamber where a vacuum lid is provided. If the vacuum lid is opened, in this situation, to introduce the optical disk substrate, the object to be treated, into the vacuum chamber, the cylinder must tolerate an atmospheric pressure pushing down the susceptor. Since the atmospheric pressure pushing the cylinder amounts to a value ranging from 1270 to 1470 Newton (N), the high-pressure air cylinder or the oil pressure cylinder is used.
The lift mechanism further needs a vacuum seal because a part of the mechanism such as cylinder rod extends into a vacuum vessel forming the chamber. An O-ring seal or a bellows seal is used for the vacuum seal. The bellows seal is composed of metallic diaphragms being piled up and welded is mounted between the cylinder rod and the lift mechanism of the vacuum apparatus.
Since the lift mechanism uses the high-pressure air cylinder or the oil pressure cylinder with large space, the vacuum apparatus, therefore, becomes large. Furthermore, the O-ring seal wears severely because metallic cylinder rod slides inside the O-ring, which is furnished on the vacuum vessel and into which, a part of the lift mechanism is extended. The wear of the O-ring seal breaks the vacuum seal at the point the wear occurred, and thus hermetic seal of the vacuum vessel cannot be maintained. Although vacuum grease has been conventionally used to prevent the wear and to improve the sealing ability, peeled off film materials or broken pieces of the disk substrate are caught in the grease to be a cause of breaking vacuum seal. Furthermore, ingredients of this grease sometimes splashed in the vacuum vessel and were mixed in the film component formed on the treating object while the vacuum apparatus operates, which gave a bad influence upon a property of the film.
With respect to the bellows seal, on the other hand, fatigue occurs in a metal during a long time use since the metallic diaphragm stretches and contracts according to the reciprocate motion between the cylinder and the rod, which suddenly causes a damage in the bellows and leads to the break of the vacuum seal.
Therefore, it is an object of the present invention to provide a small and compact lift mechanism without any means or mechanism for the vacuum seal and to provide a vacuum apparatus having such lift mechanism.